I don't think Unohana shikai heals. When you think about it her Minazuki in shikai form has fluids in its stomach that heals. I think that is the spring water from that one dude from the royal guards. In this latest chapter i noticed that she never released her shikai so she must have fought Zaraki with her zanpaktou unreleased. I also noticed that she said that she had to master her "kaidou" which means healing kido, so her shikai shouldn't be able to heal. She was healing herself and Zaraki this whole time with kido and not shikai. Her bankai is not an illusion but it melts everything her surroundings, herself, and her enemies, she just use kido to heal herself and Zaraki. I do believe she is dead, yes kubo does like to fool around with the whole cheating death crap but not this time i don't think. If you think about it he killed off Gin Ichimaru who also had a Bankai that is devastating, and he also had little background until we learned his story right before his death. I always loved Gin, and Unohana they were my favorite characters, as well as Shinji and Uryu. I conclude that Shinji may take the place as the number one healer bc it is referenced that he knows a thing or two about healing even though he may not be as experienced as Unohana